That set him on another collision course with the country's judiciary after he promised last month to bring back to court officials of the former regime acquitted of organising an attack on protesters during last year's uprising against the ousted leader Hosni Mubarak.

Mr Mursi’s decisions were announced on the eve of a planned mass protest after four days of violent demonstrations in Cairo. The demonstrators include youth groups who say Mr Mursi and his government have not fulfilled the aims of the protesters who ousted Hosni Mubarak, or brought to justice those responsible for killing protesters.

‘‘Today is the start for truly avenging the blood of the martyrs with which we have been entrusted,’’ Mr Mursi said on his official Twitter account.

Only a day earlier Mr Mursi was hailed by the US President, Barack Obama, and other leaders for his role in realizing a truce between Hamas and Israel. As well as dealing with the Gaza conflict and a renewed push to raise Egypt’s profile in the region, he is contending with unrest at home and an economy battered by months of strikes and protests.

In his pronouncements on Thursday the President ordered "new investigations and retrials" in the cases dealing with the deaths of protesters, a decision that could affect senior military officials.

He said no judicial body could dissolve the upper house of parliament or the Islamist-dominated constituent assembly that is writing a new constitution and which has been criticised by the secular-minded opposition for failing to represent all segments of society.

He has also given the body – which was due to issue a draft constitution in December – two extra months to come up with a charter, which will then be put to a referendum.

The declaration is aimed at "cleansing state institutions" and "destroying the infrastructure of the old regime".

Mr ElBaradei, the Nobel laureate and former UN atomic energy agency chief, said the declaration effectively put the President above judicial oversight.

"Mursi today usurped all state powers and appointed himself Egypt's new pharaoh. A major blow to the revolution that could have dire consequences," Mr ElBaradei wrote on Twitter.

Analysts and activists such as Gamal Eid, a human rights lawyer, predicted the decrees could further stoke unrest. ‘‘Mursi has committed a fatal mistake by decreeing his decisions cannot be appealed,’’ Mr Eid said. ‘‘The move will trigger more anti-government protests and will increase public frustration. The people don’t need another dictator.’’

Even before the announcement was read out, Islamists had gathered outside the High Court in central Cairo demanding the "cleansing of the judiciary".

Mr Mursi, who belongs to the powerful Muslim Brotherhood, is the first elected president after the popular uprising that toppled Mr Mubarak last year.

‘‘These are revolutionary decisions that came in response to peoples’ demands and will definitely gain popular support,’’ Mahmoud Ghozlan, a spokesman for the Brotherhood, said. ‘‘People have been calling for eliminating corruption and purging the judiciary since Mursi’s appointment. The decisions will bring stability and that’s what people want.’’

Agence France-Presse, Bloomberg

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